Overview
- Reports spiked on Thursday, Nov. 12, with outage tracker Downdetector logging roughly 130,000 Outlook problem reports and errors spreading to about 74 countries within an hour.
- Microsoft confirmed Exchange Online mailboxes and multiple 365 services including Teams, SharePoint Online, Copilot 365 and Defender XDR were affected and issued incident EX1550543 for administrators.
- The company says the disruption was driven not by higher user traffic but by many servers becoming unexpectedly unavailable and failing automated health checks, which shifted load onto remaining machines.
- Engineers have paused deployments, redistributed traffic, restarted affected servers, validated an alternative health-check method and prepared automated restart systems, but those measures have produced only limited and uneven recovery.
- The outage hit businesses and government users harder than many personal accounts, disrupted AI connectors used by OpenAI and Anthropic, prompted official monitoring, and adds to repeated 2026 service interruptions that highlight risks from concentrated cloud dependence.